Many current clinical guidelines recommend that assessment of osteoporosis or low bone mass, as defined by the World Health Organization (WHO), be based on bone mineral density (BMD) at the femur neck region of the proximal femur (hip). The data on the prevalence of osteoporosis in the population by age, sex, and race and ethnicity are acquired by the National Health and Nutrition Examination Survey (NHANES), a population based survey and physical assessment carried out in mobile examinations centers that are moved around the United States for sampling on a 2-year cycle. These data are an important component of the Healthy People 2020 tracking of the health of Americans. NIAMS has collaborated with the National Center for Health Statistics (NCHS)/Centers for Disease Control and Prevention (CDC) in funding the osteoporosis component of NHANES. These assessments of a population based sample have provided the BMD data used in DXA databases to determine the fracture risk status of individuals, as well as the information needed to track the state of bone health in America.